Explanation: Spread spectrum is a modulation technique that spreads the transmitted signal over a much wider frequency band than the minimum bandwidth required. Frequency Hopping Spread Spectrum (FHSS) is a specific type of spread spectrum where the carrier frequency rapidly changes according to a pseudorandom sequence known to both transmitter and receiver. This technique can involve a single carrier hopping across a range of frequencies or multiple simultaneous carriers each hopping independently or in a coordinated manner. It provides resistance to interference and jamming, and enhances security. SSB (Single Sideband) and FM (Frequency Modulation) are conventional modulation types that transmit on a single, generally fixed, carrier frequency. While FM's instantaneous frequency changes with the modulating signal, it does not "hop" across a wide, pre-defined spectrum like FHSS. OFSK (Orthogonal Frequency Shift Keying) is a digital modulation method that uses multiple fixed frequencies to encode data but is not a spread spectrum technique involving pseudorandom frequency hopping for interference rejection or security.